THE AXILLAR Y ARTER Y 639 



RELATIONS OF THE THIRD PORTION* OF THE AXILLARY ARTERY. 



In front. 



Integument and fascia. 

 Pectoralis major. 

 Inner head of median nerve. 

 Internal cutaneous nerve. 



Outer side. f N. Inner side. 



Coracobrachialis. I ^Art''^ ) Ulnar nerve. 



Median nerve. I Third portion, y Axillary vein. 



Musculocutaneous nerve. V / Lesser internal cutaneous nerve. 



Behind. 

 Subscapularis. 



Tendons of Latissimus dorsi and Teres majoi. 

 Musculospiral and circumflex nerves. 



Peculiarities. The axillary artery, in about one case out of every ten, gives off a large 

 branch, which forms either one of the arteries of the forearm or a large muscular trunk. In the 

 first set of cases this artery is most frequently the radial (1 in 33), sometimes the ulnar (1 in 72) 

 and, very rarely, the interosseous (1 in 506). In the second set of cases the trunk has been 

 found to give origin to the subscapular, circumflex, and profunda arteries of the arm. Some- 

 times only one of the circumflex, or one of the profunda arteries, arises from the trunk. In 

 these cases the brachial plexus surrounded the trunk of the branches and not the main vessel. 



Surface Marking. The course of the axillary artery may be marked out by raising the 

 arm to a right angle with the body and drawing a line from the middle of the clavicle to the 

 point where the tendon of the Pectoralis major crosses the prominence caused by the Coraco- 

 brachialis as it emerges from under cover of the anterior fold of the axilla. The third portion 

 of the artery can be felt pulsating beneath the skin and fascia, at the junction of the anterior 

 with the middle third of the space between the anterior and posterior folds of the axilla, close to 

 the inner border of the Coracobrachialis muscle. 



Applied Anatomy. Compression of the vessel may be required in the removal of tumors 

 or in amputation of the upper part of the arm; and the only situation in which this can be effect- 

 ually made is in the lower part of its course; by pressing on it in this situation from within 

 outward against the humerus the circulation may be effectually arrested. 



With the exception of the popliteal, the axillary artery is perhaps more frequently lacerated 

 than any other artery in the body by violent movements of the extremity, especially in those 

 cases where its coats are diseased. It has occasionally been ruptured in attempts to reduce old 

 dislocations of the shoulder-joint. This accident is most likely to occur during the preliminary 

 breaking -down of adhesions, in consequence of the artery having become fixed to the capsule 

 of the joint. Aneurism of the axillary artery is of frequent occurrence, a large percentage of 

 the cases being traumatic in their origin, due to the violence to which the vessel is exposed in 

 the varied, extensive, and often violent movements of the limb. 



The application of a ligature to the axillary artery may be required in cases of aneurism of 

 the upper part of the brachial or as a distal operation for aneurism of the subclavian ; and there 

 are only two situations in which the vessel can be secured rviz., in the first and in the third 

 parts of its course; for the axillary artery at its central part is so deeply seated, and, at the same 

 time, so closely surrounded with large nerve trunks, that the application of a ligature to it in 

 that situation would be almost impracticable. 



In the third part of its course the operation is most simple, and may be performed in the 

 following manner: The patient being placed on a bed and the arm separated from the side, with 

 the hand supinated, an incision about two inches in length is made through the integument 

 forming the floor of the axilla, the cut being a little nearer to the anterior than the posterior 

 fold of the axilla. After carefully dissecting through the areolar tissue and fascia, the median 

 nerve and axillary vein are exposed; the former having been displaced to the outer and the 

 latter to the inner side of the arm, the elbow being at the same time bent, so as to relax the 

 structures and facilitate their separation, the ligature may be passed around the artery from the 

 ulnar to the radial side. 



This portion of the artery is occasionally crossed by a muscular slip, the axillary arch, derived 

 from the Latissimus dorsi, which may mislead the surgeon during an operation. The occasional 

 existence of this muscle fasciculus was spoken of in the description of the muscles. It may 

 easily be recognized by the transverse direction of its fibres. 



